This invention relates to power line post insulators, and particularly to line post insulators with means for sensing currents in conductors of power systems.
Power line post insulators sometimes utilize a coil in the vicinity of the current carrying conductor to sense the conductor's currents. While such sensors generally exhibit good sensitivity they are susceptible to noise from voltages induced by adjacent conductors, such as may exist in multi-phase systems. Toroidal coils have been suggested to overcome noise. Such sensors display excellent sensitivity and noise rejection but must surround the conductor and also are excessively bulky for use in a line post insulator.
U.S. Pat. Nos. 4,700,123 and 4,859,925 of Thomas Beling, disclose line post insulators each having two current sensors that respond to currents in a conductor of a power system. According to these patents insulator housing surrounds two sensing coils on one side of the power conductor and the coils are connected subtractively to limit the noise generated by adjacent power lines in a multi-phase power system.
Such devices exhibit good rejection of noise from adjacent power lines but are comparatively insensitive because of the subtractive connection of the coils. They cause relatively high errors when used with power conductors whose diameters depart excessively from a predetermined diameter.